Multiple-stage cascade hydrorefining of contaminated charge stocks



y 2, 1967 J.T. FORTMAN 3,317,419

MULTIPLE-STAGE CASCADE HYDROREFINING OF CONTAMINATED CHARGE STOCKS FiledJune 1, 1964 Nap/7M0 Fract/'onafor\ Light Ends /v "1 Nap/2M0 "3 ,g "3

Separator & w "3 Kemsene Fracf/ona/0r v la v, A I Kerosene a Q Q w v 7)5 1 I] g: I Gas 017/ .Separa/or 0 1 Q Heater w m //vv v TOR: John T.For/man #L BY: D/sf/l/a/e Fracfionafor 4 f Golrer Disf/l/a/e A 7'TOR/VEYS United States Patent MULTIPLE-STAGE CASCADE HYDROREFINING 0FCONTAMINATED CHARGE STOCKS John T. Fortman, Des Plaines, Ill., assignorto Universal Oil Products Company, Des Plaines, Ill., a corporation ofDelaware Filed June 1, 1964, Ser. No. 371,389 14 Claims. (Cl. 208-97) Ina broad application, the present invention relates to a process for thecatalytic hydrorefining of hydrocarbons, mixtures of hydrocarbons,various hydrocarbon fractions and hydrocarbon distillates, for thepurpose of removing diverse contaminants therefrom and/ or reacting suchhydrocarbons to improve the chemical and physical characteristicsthereof. More specifically, the process described herein is directedtowards the selective hydrorefining of full boiling range hydrocarbonfractions severely contaminated by the inclusion of excessive quantitiesof nitrogenous and sulfurous compounds, and, in many instances, by thepresence of high and low-boiling unsaturated hydrocarbons. The processof the present invention is particularly advantageous in thehydrorefining of contaminated high-boiling hydrocarbon fractions, whilesimultaneously converting at least a portion of the high-boilinghydrocarbons into lower-boiling hydrocarbon products; through the use ofparticular operating conditions and techniques, the formation of cokeand other heavy carbonaceous material, otherwise resulting from thehydrorefining of such hydrocarbon fractions and/or distillates, iseffectively inhibited While achieving the desired end result.

In the present specification and appended claims, the various termshydrocarbons, hydrocarbon fractions, hydrocarbon distillates, andhydrocarbon mixtures, are intended to be synonymous, and connote varioushydrocarbons and mixtures of hydrocarbons for use as charge to thepresent process, and which may result from diverse conversion processes,or from the fractionation or initial distillation of various crude oils.Such processes include the catalytic and/or thermal cracking ofpetroleum, the destructive distillation of wood or coal, coking,shale-oil retorting, etc., and yield various hydrocarbon mixtures whichmay be advantageously employed as fuels, lubricants, and petro-chemicalmaterials, or as charge stocks in subsequent processes designed for theproduction of such petroleum products. Such hydrocarbon distillatefractions frequently contain impurities which must necessarily beremoved before the distillate fractions are suitable for their intendeduse, or which, when removed, enhance the value of distillate fractionsfor further processing. These impurities, or contaminating influences,include sulfurous compounds, nitrogenous compounds, oxygenatedcompounds, and various metallic contaminants which cause the hydrocarbondistillates to exhibit corrosive tendencies and be unstable, therebymaking them less desirable for further utilization as a fuel orlubricant.

Depending upon the intended use of a given hydrocarbon fraction ordistillate, various components thereof may be considered ascontaminating influences. For example, a naphtha fraction, intended foruse as a motor fuel, motor fuel blending component, or as a charge stockto a catalytic reforming unit, is considered to be con taminated by theinclusion therein of monoand diolefinic straight and/or branched-chainhydrocarbons. Similarly, the presence of high-boiling unsaturatedhydr-ocarbons in a charge stock intended for conversion intolower-boiling hydrocarbons, is considered a contaminating influence dueto the propensity thereof to polymerize and/or copolymerize whereby amore refractory material, much less susceptible to conversion, and moreprone ICC to deactivate catalyst, is formed. In many instances, monoandpolynuclear aromatic hydrocarbons are contaminating influences withrespect to a charge stock intended for a cracking process, since thehigher the concentration of aromatic hydrocarbons, the more refractorythe charge stock, and the higher the required severity of operation;this obviously results in the excessive production of coke andcabonaceous material, as Well as excessive quantities of waste gasesincluding light paraflinic hydrocarbons. Similarly, fuel oils containingexcessive quantities of aromatic hydrocarbons exhibit poor burningqualities and a low smoke point whereby the products of combustion havea greater tendency to cause severe pollution of the atmosphere.

Probably the most prevalent of the aforementioned impurities is combinedsulfur which may exist in the hydrocarbon fraction as a sulfide,mercaptan, or as thiophenic sulfur, etc. Although existing in one ormore of these, or other forms, the concentration of the sulfur isgenerally expressed as if existing as the element thereof. The presenceof sulfurous compounds, regardless of the exact boiling range thereof,results in the relatively rapid deactivation of some catalyticallyactive metallic components. The deactivation appears to result from thereaction of the sulfurous compounds with various catalytic components,the extent of such deactivation increasing as the process continues, andthe charge stock further contaminates the catalyst through contacttherewith. Sulfurous compounds are generally removed by the process ofdestructive hydrodesulfurization, wherein the sulfur-bearing molecule istreated at an elevated temperature, generally in excess of about 650 F.,whereby there occurs a cracking of the sulfur-carbon bond which, in thepresence of hydrogen, results in the conversion to hydrogen sulfide anda hydrocarbon. The difficulty with which a particular sulfurous compoundis thus destructively removed, is generally dependent upon theparticular boiling range thereof, the difliculty increasing as theboiling point increases. Similarly, nitrogenous compounds are treated,in the presence of hydrogen, such that there exists a cracking of thenitrogen-carbon bond, whereby the nitrogenous compound is converted intoammonia and a hydrocarbon. In general, the conversion, by a suitablehydrorefining process, of the nitrogenous compounds into ammonia andhydrocarbons is more difficult to achieve to an acceptable degree thanthe conversion of the sulfurous compounds into hydrogen sulfide andhydrocarbons. Furthermore, the presence of highboiling nitrogenouscompounds appears to affect adversely the activity of a particularhydrorefining catalyst with respect to the destructive removal ofsulfurous compounds, notwithstanding that the latter reaction isgenerally more easily achieved.

When existing in some combined form, oxygen offers less of a removalproblem than sulfur. Under the operating conditions employed, oxygenatedcompounds are relatively easily converted to the hydrocarbon counterpartand 'water, the latter being removed from the hydrocarbon productefiluent by any well-known, suitable separation means.

In addition to the above-described contaminants, hydrocarbon distillatesresulting from the various conversion processes hereinbefore set forth,contain an appreciable quantity of unsaturated hydrocarbons, includingboth mono-olefinic and di-olefinic hydrocarbons, and aromatics,including compounds such as styrene, isoprene, dicyclopentadiene, etc.When these highly unsaturated distillates are subjected to hydrorefiningfor the purpose of removing the sulfurous and nitrogenous compounds,there frequently is encountered the difliculty of effecting the desireddegree of reaction due to the formation of coke and other heavyhydrocarbonaceous material. The deposition of coke and othercarbonaceous material appears to be an inherent result of the necessityto effect the destructive removal of sulfurous and nitrogenous compoundsat elevated temperatures above about 650 F. Various heaters andmiscellaneous appurtenances of the conversion zone experience heavycoking, which appears as a formation of solid, highly carbonaceousmaterial, and results from the thermal reaction of the unstable orcoke-forming compounds within the hydrocarbon distillate being chargedto the unit. In addition, polymerization and copolymerization of themonoand di-olefins is effected within the reaction zone, and to theextent that the catalyst disposed there in becomes shielded, by gummypolymerization products, from the hydrocarbon distillate beingprocessed.

As hereinbefore set forth, dependent upon the particular charge stockand/ or the intended use of the product to be derived therefrom, monoandpolynuclear aromatics may be considered as contaminating influences. Forexample, an unrefined gas oil, derived from a topped or reduced crude,and having a boiling range from about 500 F. to about 850 F., containsin excess of about 60.0% by volume of aromatic hydrocarbons, and as suchis considered too refractory for use as charge to a catalytic crackingprocess.

An abundance of hydrocarbon charge stocks, otherwise suitable forsubsequent processing, currently exists wherein the same arecontaminated through the presence of excessive quantities of all four ofthe foregoing described contaminating influences. That is, a largevolume of hydrocarbon fractions and distillates are available, however,contaminated by the presence of excessive quantities of sulfurouscompounds, nitrogenous compounds, monoand di-olefinic hydrocarbons, andmonoand polynuclear aromatic hydrocarbons. Since the operatingconditions required to effect suitable decontamination with respect to agiven contaminating influence, are not necessarily those which likewiseeffect a suitable degree of decontamination with respect to anothercontaminating influence, it is very difficult to process such chargestocks in a manner which results in an acceptably hydrorefined productefiluent.

' For example, a hydrorefining process which is conducted underconditions of temperature and pressure to produce a substantiallysaturated product efiluent significantly reduced in aromatic content,the liquid yield of such effiuent is decreased as a result of theover-production of normally gaseous hydrocarbons, inherently resultingfrom the undesirable cracking of the lower-boiling components of thehydrocarbon charge stock. Also, as hereinbefore set forth, temperatureswhich are necessary to produce a substantially sulfur and nitrogen-freeproduct effluent, will generally result in the excessive polymerizationand copolymerization of the monoand di-olefinic hydrocarbons, even priorto entering the reaction zone to contact the catalyst disposed therein.

The object of the present invention is to provide a hydrorefiningprocess particularly adaptable for effecting the decontamination of ahydrocarbon charge stock, boiling at least in part at temperatures abovethe normal gasoline boiling range, and contaminated by the presence ofexcessive quantities of nitrogenous and sulfurous compounds, and whichmay be further contaminated by the inclusion therein of excessivequantities of monoand di-olefinic hydrocarbons, as well as monoandpolynuclear aromatic hydrocarbons. Another object of the presentinvention is to permit the processing of a highly contaminated, fullboiling range hydrocarbon charge stock to produce a varied andparticular product distribution, various desired fractions of such totalproduct meeting relatively rigid specifications with respect to theforegoing described contaminating influences.

The applicability of the present invention, as set forth in thefollowing embodiments thereof, to the production of substantiallycontaminant-free hydrocarbon products, may be more clearly understood byinitially defining several of the terms and phrases employed within theembodiments, the specification, and the appended claims. In thoseinstances where temperatures are given in regard to initial boilingpoints, boiling ranges and end boiling points it is understood that thetemperatures have reference to those which are obtained through the useof standard ASTM Distillation Methods. The term, hydrocarbons, connotessaturated hydrocarbons, straight-chain and branched-chain hydrocarbons,unsaturated hydrocarbons, aromatic hydrocarbons, naphthenichydrocarbons, as well as various mixtures thereof including hydrocarbonfractions and/or hydrocarbon distillates. The phrase, hydrocarbonsboiling within the gasoline boiling range, or gasoline fraction, orgasoline boiling range hydrocarbons, is intended to connote thosenormally liquid hydrocarbons boiling at a temperature of from F. toabout 400 F. or 450 F.; that is, hydrocarbon fractions having an initialboiling point above about 100 F. and an end boiling point less thanabout 450 R, which hydrocarbons are generally employed as motor fuels,and which may contain isoand normal butanes and/ or pentanes, as thecase may permit. Hydrocarbons boiling at temperatures above the gasolineboiling range, or, kerosene fraction, or middle-distillate hydrocarbons,refers, therefore, to hydrocarbons and hydrocarbon fractions having aninitial boiling point of from about 350 F. to about 450 F. and an endboiling point of about 500 F. to about 650 F., which hydrocarbonfractions are generally utilized as fuel oils, jet fuel, kerosene, etc.In some localities, kerosene fractions command a greater market value,than a gasoline fraction, due to the demand for great volumes oflowboiling fuel for both heat and light. Thus, in these instances, akerosene fraction will have an initial boiling point as low as about 300F. It is intended that such fractions be included within the broad scopeof the present invention. The term, gas oil, or hydrocarbons boilingabove the middle-distillate boiling range, is intended to describe ahydrocarbon fraction and/ or distillate having an initial boiling pointof from as low as 400 F. to about 650 F. (generally, these fractionshave an initial boiling point of at least about 500 F.), and an endboiling point within the range of about 800 F. to about 950 F., andwhich hydrocarbons may be employed at least in part as diesel oil,distillate fuel, charge stock to catalytic cracking processes and/ orhydrocracking processes, etc.

Similarly, in regard to the catalytic composite em ployed within thevarious reaction zones of the process of the present invention, theterm, metallic component, or catalytically active metallic component, isintended to encompass those catalytic components which are employed fortheir hydrorefining and/or hydrocracking activity, as well ashydrogenation activity with respect to unsaturated hydrocarbons, as thecase may be. In this manner, the catalytically active metalliccomponents are distinguished from those components which are employedprimarily as an integral part of the carrier material. As hereinafterset forth in greater detail, the process of the present inventionutilizes a catalytic composite consisting of at least four components inparticular concentrations. In a broad embodiment, the present inventionrelates to a process for hydrorefining a hydrocarbon charge stockboiling above the gasoline boiling range and containing a contaminantselected from the group consisting of nitrogenous compounds andsulfurous compounds, which process comprises the steps of: (a) reactingsaid charge stock and hydrogen at hydrorefining conditions in a firstreaction zone containing a hydrorefining catalytic composite; (b)separating the normally liquid product effluent from said first reactionzone into a first light fraction having an end boiling point of fromabout 500 F. to about 650 F., and a hydrorefined first heavy fraction;(0) combining at least a portion of said first light fraction with ahydrocarbon mixture having an initial boiling point of from about 350 F.to about 450 F. and containing at least one of the aforesaidcontaminants, and reacting the resulting mixture with hydrogen athydrore of from about 350 fining conditions in a second reaction zonecontaining a hydrorefining catalytic composite; (d) separating thenormally liquid product effiuent from said second reaction zone into asecond light fraction, having an end boiling point within the range offrom about 350 F. to about 450 F., and a hydrorefined second heavyfraction; (e) combining at least a portion of said second light fractionwith a hydrocarbon mixture, having an end boiling point F. to about 450F. and containing at least one of the aforesaid contaminants, reactingthe resulting mixture with hydrogen at hydrorefining conditions in athird reaction Zone containing a hydrorefining catalytic composite; and,(f) separating the product effluent from said third reaction zone into anormally gaseous phase and a hydrorefined third heavy fraction.

Anotherbroad embodiment of the present invention encompasses a processfor hydrorefining a hydrocarbon charge stock boiling above the gasolineboiling range and containing a contaminant selected from the groupconsisting of nitrogenous compounds and sulfurous compounds, whichprocess comprises the steps of: (a) separating said charge stock into agasoline fraction having an end boiling point Within the range of fromabout 350 F. to about 450 F., a kerosene fraction having an end boilingpoint of as low as about 400 F. to about 650 F., and a heavy bottomsfraction; (b) reacting said heavy bottoms fraction with hydrogen athydrorefining conditions in a first reaction zone containing ahydrorefining catalytic composite; (c) separating the normally liquidproduct effluent from said first reaction zone into a first lightfraction having an end boiling point of as low as about 400 F. to about650 F. and a hydrorefined substantially sulfur-free heavy fraction; (d)combining at least a portion of said first light fraction with theaforesaid kerosene fraction and reacting the resulting mixture withhydrogen at hydrorefining conditions in a second reaction zonecontaining a hydrorefining catalytic composite; (e) separating thenormally liquid product efiiuent from said second reaction zone into asecond light fraction having an end boiling point of from about 350 F.to about 450 F. and a hydrorefined substantially sulfurfree keroseneproduct; (f) combining at least a portion of said second light fractionwith the aforesaid gasoline fraction and reacting the resulting mixturewith hydrogen at hydrorefining conditions in a third reaction zonecontaining a hydrorefining catalytic composite; and, (g) separating theproduct effluent from said third reaction zone into a normally gaseousphase and a substantially sulfur and nitrogen-free hydrorefined gasolineproduct. A more limited embodiment of the present invention involves aprocess for hydrorefining a hydrocarbon charge stock boiling above thegasoline boiling range and containing sulfurous and nitrogenouscompounds, which process comprises the steps of: (a) separating saidcharge stock into a gasoline fraction having an end boiling point withinthe range of from about 350 F. to about 450 F., a kerosene fractionhaving an end boiling point of from about 500 F. to about 650 F., and aheavy bottoms fraction; (b) reacting said heavy bottoms fraction withhydrogen at hydrorefining conditions selected to convert nitrogenous andsulfurous compounds to ammonia, hydrogen sulfide and hydrocarbons, in afirst reaction zone containing a hydrorefining catalytic composite; (c)separating the normally liquid product eflluent from said first reactionzone into a first light fraction having an end boiling point of fromabout 350 F. to about 450 F. and a second light fraction having an endboiling point of from about 500 F. to about 650 F. and a hydrorefined,substantially sulfur-free heavy fraction; (d) combining at least aportion of said second light fraction with the aforesaid kerosenefraction and reacting the resulting mixture with hydrogen athydrorefining conditions selected to convert nitrogenous and sulfurouscompounds to ammonia, hydrogen sulfide and hydrocarbons, in a secondreaction zone containing a hydrorefining catalytic composite; (e)separating the normally liquid product efiiuent from said secondreaction zone into a third light fraction having an end boiling point offrom about 350 F. to about 450 F. and a hydrorefined, substantiallysulfurfree kerosene product; (f) combining at least a portion of each ofsaid first and third light fractions with the aforesaid gasolinefraction and reacting the resulting mixture with hydrogen athydrorefining conditions selected to convert nitrogenous and sulfurouscompounds to ammonia, hydrogen sulfide and hydrocarbon in a thirdreaction zone containing a hydrorefined catalytic composite; and, (g)separating the product efiluent from said third reaction zone into anormally gaseous phase and a substantially sulfur and nitrogen-freehydrorefined gasoline product.

A more limited embodiment of the present invention affords a process forhydrorefining a full boiling range coker distillate containing sulfurousand nitrogenous compounds, which process comprises the steps of: (a)separating said distillate into a gasoline fraction having an endboiling point Within the range of from about 350 F. to about 450 F., akerosene fraction having an end boiling point of from about 500 F. toabout 650 F., and a heavy bottoms fraction having an initial boilingpoint of from about 500 F. to about 650 F.; (b) reacting said heavybottoms fraction with hydrogen present in an amount of about 1000 toabout 6000 s.-c.f./bbl., at hydrorefining conditions including a maximumcatalyst temperature within the range of from about 600 F. to about 850F. and selected to convert sulfurous and nitrogenous compounds tohydrogen sulfide, ammonia and hydrocarbons, in a first reaction zonecontaining a hydrorefining catalytic composite of alumina, from about12.0% to about 40.0% by Weight of silica, molybdenum and nickel; (c)removing hydrogen sulfide and ammonia from the product effluent fromsaid first reaction zone, separating the remaining normally liquidproduct into a first light fraction having an end boiling point of fromabout 350 F. to about 450 F., a second light fraction having an endboiling point of from 500 F. to about 650 F. and a hydrorefined,substantially sulfur-free gas oil fraction; (d) combining at least aportion of said second light fraction with the aforesaid kerosenefraction, reacting the resulting mixture with hydrogen present in anamount of from about 1000 to about 6000 s.c.f./bbl., at hydrorefiningconditions including a maximum catalyst temperature lower than that insaid first reaction zone, and selected to convert sulfurous andnitrogenous compounds to hydrogen sulfide, ammonia and hydrocarbons, ina second reaction zone containing a hydrorefining catalytic composite ofalumina, from about 10.0% to about 25.0% by weight of silica, molybdenumand nickel; (e) removing hydrogen sulfide and ammonia from the producteffluent from said second reaction zone, separating the remainingnormally liquid product into a third light fraction having an endboiling point of from about 350 F. to about 450 F. and a hydrorefined,substantially sulfur-free kerosene fraction; (f) combining at least aportion of each of said first and third light fractions with theaforesaid gasoline fraction and reacting the resulting mixture withhydrogen present in an amount of from about 1000 to about 6000s.c.f./bbl., at hydrorefining conditions including a maximum catalysttemperature of from about 600 F. to about 850 F. and selected to convertsulfurous and nitrogenous compounds to hydrogen sulfide, ammonia andhydrocarbons, in a third reaction zone containing a hydrorefiningcatalytic composite of alumina, silica, molybdenum and nickel; and, (g)separating the product elfiuent from said third reaction zone into anormally gaseous phase containing hydrogen sulfide and ammonia, and asubstantially sulfur and nitrogen-free hydrorefined gasoline fraction.

From the foregoing embodiments, it will be noted that the cascadesystem, encompassed by the present invention, is a multiple-stageprocess for eifectin-g the hydrorefining of hydrocarbon charge stockscontaining hydrocarbons boiling at temperatures above the normalgasoline boiling range. The particularly preferred charge stocks, forutilization in the cascade system, are those which are referred to asfull boiling range charge stocks. A full boiling range charge stock isconsidered to be one which contains a significant percentage ofhydrocarbons having boiling points above a temperature of 650 F., aquantity of hydrocarbons boiling within the kerosene, ormiddle-distillate boiling range, and some hydrocarbons boiling Withinthe normal gasoline boiling range. For example, a full boiling rangecoker distillate will contain a heavy bottoms fraction having an initialboiling point of about 650 F. in an amount of 26.0 volume percent, amiddle-distillate fraction having an initial boiling point of about 450F. in an amount of about 47.0% by volume and a gasoline fraction havingan initial boiling point of from about 100 F. to about 125 F. in anamount of about 37.0% by volume. Thus, full boiling range charge stocks,to which the process of the present invention is particularly adaptable,include, but not by way of strict limitation, various gas oils, a widevariety of coker distillates, deasphalted crude oils, fuel oil stocks,catalytically and thermally-cracked stocks, etc. In accordance with thecascade system, each specific fraction of the charge stock is subjectedto selective conditions in a specific reaction zone, after which thedesired product is removed, the remainder being combined with anotherspecific fraction for reaction at other selective conditions, and so onuntil the entire charge stock has been incrementally processed at themost advantageous conditions conducive to the attainment of the desiredend result. As hereinafter indicated by specific example, this step-wiseprocessing results in a volumetric yield in excess of 100.0%, and inmost instances from about 2.0% to about 15.0% greater than the volume ofcharge stock processed in a given time interval. The unusual economicaladvantages of increased volume, while simultaneously producingcontaminant-free products, will be readily recognized by thosepossessing skill within the art of petroleum refining and processingtechniques.

Through the utilization of the cascade system of the present invention,a desirable degree of selective hydrocracking is effected in the variousstages with the result that the higher molecular weight components ofthe full boiling range charge stock are converted into lowerboiling,normally liquid hydrocarbon products, without the usual accompanyingconversion to light gaseous hydrocarbons. Since the operating conditionsWithin each of the reaction zones are specifically selected inaccordance with the physical and chemical characteristics of the chargestock passing therethrough, the degree of hydrocracking effected in agiven reaction zone is such that excessive quantities of light, normallygaseous hydrocarbons are not produced at the expense of more valuableliquid hydrocarbon products.

Hydrocracking, or destructive hydrogenation, as distinguished from theaddition of hydrogen to unsaturated bonds between carbon atoms(hydrogenation), and the destructive removal of nitrogen and sulfur bysplitting the sulfur-carbon and nitrogen-carbon bonds, effects definitechanges in the molecular structure of hydrocarbons. Hydrocracking isdesignated as a cracking under hydrogenation conditions such thatlower-boiling products of a more saturated nature result than whenhydrogen is not present. Regardless of the degree of hydrocrackingintended, and, in the process of the present invention, hydrorefiningreactions are of primary concern, in order to assure effective catalyticaction over an extended period of time, and from the standpoint ofproducing the increased yield of liquid product having improved physicaland/ or chemical characteristics, controlled or selective cracking isdesirable. Controlled or selective hydrocracking results in an increasedyield of middle-distillate boiling range hydrocarbons which aresubstantially free from high molecular weight unsaturated hydrocarbons.The necessity for selectivity exists in order to avoid the decompositionof normally liquid hydrocarbons substantially or completely intonormally gaseous hydrocarbons, the latter being inclusive of methane,ethane and propane. Hydrocracking reactions which are permitted to runrampant can affect seriously the economic considerations of a givenprocess, particularly in view of the fact that uncontrolledhydrocracking results in a more rapid formation of increased quantitiesof coke and other heavy carbonaceous material which becomes depositedupon the catalytic composite and decreases, or even destroys, theactivity thereof to catalyze the desired reactions in the desiredmanner.

Selective, or controlled, hydrocracking must also be considered wherethe primary purpose is to effect an acceptable degree of hydrorefiningof the charge stock, and particularly where the greater proportion ofsuch charge stock boils above the normal gasoline boiling range. Forexample, a full boiling range coker distillate generally contains asignificant quantity of aromatic compounds of low molecular weight andboiling within the normal gasoline boiling range. These aromaticcompounds are highly desirable as a motor fuel or motor fuel blendingcomponent, and it is, therefore, not advantageous to subject these lowmolecular weight aromatic compounds to hydrocracking, or ring-openingreactions. The cascade system of the present invention permits thehigher boiling components of the charge stock to be subjected to thedegree of severity required for suitable hydrorefining, withoutsubjecting the low molecular weight aromatic hydrocarbons to undesirablehydrocracking and/ or ring-opening reactions. The cascade system foreffecting the hydrorefining of a full boiling range hydrocarbon chargestock, further affords flexibility with respect to product distribution,and can be tailored to any desired specifications which may be imposedas a result of considering such items as marketing demands, fluctuationsin marketing value of the particular products, other processes which areinvolved in an integrated refinery operation, etc.

The rnultiple-stage, cascade hydrorefining process of the presentinvention may be more cleanly understood through reference to theaccompanying drawing which illustrates an embodiment thereof. It is notintended, however, to limit unduly the present process to a particularembodiment as indicated in this drawing. Advantages other than thosehereinhefore and hereinafter set forth, will become apparent to thosecognizant of the techniques involved in petroleum refining operations,upon reference to the drawing and the explanation following. Also, it isrecognized that many modifications may be made to the process flow,equipment, operating conditions, etc. depending upon the particulardesired end result while processing a given hydrocarbon charge stock. Itis not intended that such insignificant modifications remove the presentinvention beyond the scope and spirit of the appended claims. In thedrawing, various flow valves, control valves, coolers, condensers,overhead reflux condensers, reboilers, pumps, compressors, heaters,knockout pots, etc., have been eliminated, or greatly reduced, as notbeing essential to the complete understanding of the present invention.The utilization of these, and other miscellaneous appurtenances willimmediately be recognized by one possessing skill in the art ofpetroleum processing. It is believed that the illustrative drawingclearly and concisely sets forth the manner in which the presentinvention is effected. The explanation of the drawing as presented isset forth in more or less general terms in order to present clearly theflexible nature inherent in the cascade system for effecting thehydrorefining process; it is intended that the explanation besupplemented 'by the specific example hereinafter set forth.

With reference to the drawing, a full boiling range hydrocarbon chargestock, for example a coker distillate,

enters the process through line 1, being subjected to frac tionation indistillate fractionator 2. Fractionator 2 is employed for the purpose ofseparating the coker distillate charge stock into at least three primaryfractions, indicated as leaving fractionator 2 via lines 3, 4 and 5. Inthose instances where the fresh charge stock entering line 1 possesses aboiling range indicating an initial boiling point of about 100 F. toabout 125 F. and an end boiling point of from about 800 F. to about 850F., a gasoline fraction having an end boiling point within the range ofabout 350 F. to about 450 F. will be removed via line 5; a kerosenefraction having an end boiling point of from about 500 F. to about 650F. will be removed at some intermediate point in fractionator 2 via line4; a heavy bottoms fraction, containing that portion of the hydrocarboncharge stock boiling at temperatures above the end boiling point of thekerosene fraction, will be removed via line 3. In many applications ofthe present invention, the charge stock will have an end boiling pointabove about 850 F., and/ or an initial boiling point of from 130 F. toabout 300 F. In such situations, it is generally desirable to remove anaphtha fraction having an end boiling point of about 400 F., a kerosenefraction having an end boiling point of about 650 F. through line 4, agas oil fraction having an end boiling point of about 850 F. via line 3,which is then located at some point intermediate the charge inlet andbottom withdrawal of fractionator 2 and a heavy bottoms fractioncontaining that portion of the charge stock boiling above 850 F. In anyevent, the gas oil fraction, or heavy bottoms in line 3 is passed intoheater 6 after being admixed with a hydrogen-rich recycle gas stream inline 11. The mixture of hydrogen in line 11, and gas oil fraction inline 3, is such that the hydrogen concentration is greater than about1000 s.c.f./bbl., and preferably within the range of about 1000 to about6000 s.c.f./bbl. of liquid charge. The mixture of hydrogen andhydrocarbons entering heater 6 is raised to the operating temperaturerequired to maintain the maximum temperature of the catalyst disposed inreactor 8 within the range of about 600 F. to about 850 F., and passesthrough line 7 into reactor 8.

Reactor 8 contains a catalytic composite specifically tailored to effectthe hydrorefining of heavier hydrocarbons, while selectivelyhydrocracking at least a portion into lower-boiling normally liquidhydrocarbon products. Therefore, as hereinafter set forth in greaterdetail, the catalytic composite in reaction zone 8 comprises a siliceouscarrier material containing at least one metallic component selectedfrom Groups VIB and VIII of the Periodic Table. Reactor 8 is maintainedunder an imposed pressure of from about 500 to about 5000 p.s.i.g., andprefera-bly at an intermediate level of from about 1000 to about 3000p.s.i.g.; the liquid hourly space velocity (defined as volumes of liquidhydrocarbon charge per hour per volume of catalyst disposed within thereaction zone) will be within the range of from about 0.25 to about10.0. The total product effluent is removed from reactor 8 via line 9,and passes into separator 10. Separator 10 is utilized to provide anormally liquid hydrocarbon product and a gaseous phase; the separatoris generally maintained under the same pressure as that existing inreactor 8, allowing, obviously, for the inherent pressure drop in thesystem, and is maintained at a temperature of about 100 F. or less. Ahydrogen-rich gaseous phase is withdrawn from separator 10 via line 11by any suitable compressive means (not illustrated in the drawing),being admixed with the liquid hydrocarbon in line 3 entering heater 6.

Gaseous components other than hydrogen are removed from the normallyliquid hydrocarbons in separator 10, including hydrogen sulfide,ammonia, sulfur dioxide, various oxides of nitrogen, and some lightparaflinic hydrocarbons, and should be removed from the gas phase priorto the latter being recycled via line 11. Various modifications may bemade to the separating means illustrated by separator 10, whereby theoverall flow pattern is changed, but the function to be served, as wellas the end result, remains the same. As hereinabove set forth, theprimary function of separator 10 is to provide a hydrogenrich recyclegas stream, in line 11, to combine with the hydrocarbons in line 3, anda normally liquid product efiluent leaving separator 10 via line 12.Thus, for example, the total gaseous phase illustrated as leaving line11, may be passed through a suitable absorbent material, whereby thelight paraflinic hydrocarbons are recovered substantially free fromhydrogen sulfide and ammonia, and the various oxides of nitrogen andsulfur. Similarly, water may be injected into line 9, the mixtureentering a suitable liquid-liquid separating zone whereby the ammonia isabsorbed in, and removed with the Water phase, the light paraffinichydrocarbons and other gaseous components being removed as indicated byline 11, and the normally liquid hydrocarbons removed via line 12.Various other modifications, in regard to the separating meansillustrated by separator 10, as Well as those separating meanshereinafter described, and illustrated by separators 22 and 32, will beimmediately recognized by those possessing skill within the art ofpetroleum processing.

In any event, the normally liquid portion of the total product efiiuentfrom reactor 8 is removed from separator 10 via line 12, and isintroduced into gas oil fractionator 13. The primary purpose offractionator 13 is to provide a hydrorefined, substantially sulfur-freebottoms product, the boiling range of which will depend to a largeextent upon the purpose for which this particular product is intended.For example, in one particular embodiment, the bottoms product will havean initial boiling point of about 500 F., and an end boiling point ofabout 825 F., being a gas oil which is intended for utilization as acharge stock to a catalytic cracking unit. In many applications of thepresent invention, the bottoms product from fractionator 13 will beintended for utilization as a distillate fuel, in Which case the initialboiling point will be as high as about 650 F. As hereinafter indicatedby specific example, regardless of its intended use, the gas oil productis substantially sulfur-free, and does not contain that quantity ofnitrogenous compounds and aromatic compounds which would detrimentallyaffect such intended use.

In a particularly preferred embodiment of the present invention, akerosene fraction, having an initial boiling point within the range ofabout 350 F. to about 450 F. and an end boiling point of from about 500F. to about 650 F. is removed from fractionator 13 via line 17containing valve 17a. This fraction is admixed with the originalkerosene fraction derived from the hydrocarbon charge stock, leavingdistillate fractionator 2 via line 4, the mixture continuing throughline 4 into heater 18. The remainder of the liquid product eifluent fromreactor 8, being a naphtha or gasoline fraction having an end boilingpoint of from about 350 F. to about 450 F., is removed from fractionator13 via line 15 containing valve 15a. This gasoline fraction is admixedin line 5 with the original gasoline fraction derived from thehydrocarbon charge stock, the mixture being passed into heater 28. Inthis preferred embodiment, valve 16a in line 16 remains closed; however,in another embodiment, depending upon the quantity of gasoline boilingrange hydrocarbons originally present in the coker distillate plus thoseproduced in reactor 8, valve 16a will be open, valve 15a and 17a beingclosed. In this embodiment, that portion of the total product efiiuentwhich boils below the desired initial boiling point of the gas oilleaving via line 14, will pass via lines 15 and 16 through valve 16ainto line 4.

Prior to entering heater 18, the hydrocarbon mixture in line 4 iscombined with a hydrogen-rich recycle gas stream in line 23, theconcentration of hydrogen being greater than about 1000 s.c.f./bbl., andpreferably within the range of from about 1000 to about 6000 s.c.f/bbl.of total liquid in line 4. The mixture is raised to the operatingtemperature required to maintain the maximum temperature of the catalystdisposed in reactor 20, within the range of from 600 F. to about 850 F.,and preferably at a temperature less than the operating temperaturewithin the first reaction zone (reactor 8), leaving heater 18 via line19, and passing into reactor 20. Reactor 20 is maintained at a pressurewithin the range of from about 500 to about 5000 p.s.i.g., andpreferably from about 1000 to about 3000 p.s.i.g. The liquid hourlyspace velocity, hereinbefore defined, through reactor 20 will be withinthe range of from about 0.25 to about 10.0, but preferably at a levelgreater than that experienced in reactor 8. Although the hydrorefiningcatalytic composite, disposed in reactor 20, may be identical to thatdisposed in reactor 8, being an alumina-silica carrier material withwhich is composited at least one metallic component from the metals ofGroup VI-B anl VIII of the Periodic Table, in many instances the mode ofoperation is such that the silica content of the catalyst in reactor 20is less than that of the catalyst disposed in reactor 8, and lies Withinthe range of from about 10.0% to about 25.0% by weight.

The total product effluent from reactor 20 passes through line 21 intoseparator 22, from which a hydrogen-rich recycle gas stream is removedvia line 23 to be admixed with the kerosene fraction charge in line 4.As hereinbefore described with reference to separator 10, separator 22is employed to illustrate a separating means whereby the normally liquidhydrocarbon product from reactor 20 is recovered in line 24,substantially completely free from light paraifinic hydrocarbons andother gaseous material including hydrogen sulfide and ammonia.Similarly, the separating means illustrated by separator 22 may take anyform which is suitable for achieving the desired results; that is,treating the normally gaseous phase in line 23 to provide ahydrogen-rich recycle gas stream, and a normally liquid hydrocarbonstream substantially free from light paraffinic hydrocarbons includingmethane, ethane and propane.

The normally liquid portion of the product efiiuent from reactor 20 isremoved from separator 22 via line 24 and passes into kerosenefractionator 25. Depending upon the desired end result, the kerosenefraction which is removed from fractionator 25 via line 26 will have aninitial boiling point within the range of from 300 F. to about 450 F.and an end boiling point of from 400 F. to about 650 F. The remainingportion of the charge to fractionator 25, that is, the naphtha orgasoline fraction, is removed via line 27 to combine with the originalgasoline fraction in line 5, the latter also including the gasolinefraction obtained as an overhead product from gas oil fractionator 13,entering line through line containing valve 15a.

The mixture of gasoline boiling range hydrocarbons, having an endboiling point of from about 350 F. to about 450 F., is admixed with ahydrogen-rich recycle gas stream in line 34, the mixture continuingthrough line 5 into heater 28. The temperature of the mixture isincreased to the level necessary to maintain a maximum catalysttemperature within the range of from about 600 F. to about 850 F., andpasses through line 29 into reactor 30. Reactor 30 is maintained at alower pressure than reactors and 8, within the range of about 500 toabout 3000 p.s.i.g., and preferably within the range of from about 700to about 1500 p.s.i.g. The liquid hourly space velocity, hereinbeforedefined, will be within the range of from about 0.25 to about 10.0, andpreferably at a level greater than that through reactor 20. Thehydrorefining catalytic composite disposed within reactors 8 and 20,that is, an alumina-silica carrier material composited with at least onemetallic component from the group of metals of Groups VI-B and VIII ofthe Periodic Table. The total product efiluent from reactor 30 passesthrough line 31 into separator 32, from which the hydrogen-rich gaseousphase is withdrawn via line 34 to combine with the gasoline fraction inline 5. The hydrogenrich recycle gas stream is such that theconcentration of hydrogen is greater than 1000 s.c.f./ bbl., andpreferably within the range of from about 1000 to about 6000 s.c.f./bbl. of liquid charge. The normally liquid portion of the producteifiuent from reactor 30 is removed from separator 32 via line 33, andis introduced into naphtha fractionator 35. Naphtha fractionator 35 mayfunction as a depropanizer, debutanizer, or depentanizer, depending uponthe desired boiling range of the hydrorefined product effiuent leavingfractionator 35 via line 36. In those instances where naphthafractionator 35 functions as a debutanizer, the bottoms gasolinefraction in line 36 will contain pentanes and heavier hydrocarbons up toan end boiling point of about 350 F. to about 450 F. In other instances,depending upon the use for which the naphtha is intended, the overallrefinery operation, and other such factors, fractionator 35 may functionas a depropanizer such that the isoand normal butanes are contained inthe product naphtha fraction. As hereinafter indicated in a specificexample, the product naphtha fraction possesses the physical andchemical characteristics required of a charge stock to a catalyticreforming unit for the purpose of producing large quantities of highquality motor fuel and motor fuel blending components.

From the foregoing description of the embodiments illustrated in theaccompanying drawing, it is readily ascertained that the cascade systemof the present invention is, in effect, a multiple-stage process forproducing hydrocarbon fractions boiling within the gasoline boilingrange, the kerosene boiling range, the middle-distillate boiling rangeand the gas oil boiling range, all of which hydrocarbon fractions aresubstantially completely free from various contaminating influences, andare, therefore, suitable as charge stocks for direct, subsequentprocessing, or for immediate use as a particular petroleum product. Itis readily ascertained from the foregoing description, that the cascadesystem of hydrorefining affords the necessary flexibility to permit bothmoderate and extreme fluctuations in charge stock characteristics, aswell as in desired product quality and quantity. Various modificationsmay be made to the illustrated embodiment to adjust for changes incharge stock and desired product quality; it is not intended that suchmodifications remove the process from the scope and spirit of theappended claims. For example, as hereinabove stated in regard toseparators 10, 22 and 32, changes may be made whereby a somewhatdifferent fiow pattern and apparatus set up results. It is evident,however, that such a fiow pattern will merely accomplish the same objectresulting from the flow pattern illustrated within the drawing. Anessential feature of the cascade process of the present inventioninvolves the multiple-stage reaction zone system, whereby each stageindividually performs a particular function in a particular manner,while processing a particularly given fraction of the full boiling rangecharge stock, the combinative effect resulting in various hydrocarbonproduct fractions substantially completely free from the contaminatinginfluence of sulfurous and nitrogenous compounds.

Although the operating conditions of temperature, pres sure, hydrogenconcentration and liquid hourly space velocity, may be virtually thesame in all of the three reaction zones, that is, a maximum catalysttemperature of from about 600 F. to about 850 F., a pressure within therange of about 500 to about 5000 p.s.i.g., a preferred hydrogenconcentration of from 1000 to about 6000 s.c.f./bbl. and a liquid hourlyspace velocity of from about 0.25 to about 10.0, it is significantlymore advantageous,

in view of the cascade system, to vary the operating conditions inaccordance with the characteristics of the charge to a given reactionzone. With reference once again to the accompanying drawing, the chargeto reactor 8 may, for example, consist predominantly of gas oil fractionhydrocarbons having an initial boiling point of about 515 F. and an endboiling point of about 825 F. As

contaminating influences, this particular gas oil fraction may containnitrogenous compounds in an amount as high as about 1500 p.p.m. (asnitrogen), sulfuro-us compounds in an amount of about 3.3% by weight (assulfur), and about 60.0% by volume of polynuclear aromatic hydrocarbons.In this instance, the latter is included as a contaminating influencesince a clean gas oil fraction is generally considered as containing notmore than about 30.0% by volume of aromatic compounds when intendedeither as a distillate fuel or diesel oil, or as the charge stock to acata ytic cracking process. With respect to the concentration 01nitrogenous and sulfurous compounds, in a gas oil product, these arenecessarily low to avoid the formation of noxious gaseous material uponcombustion, and thereby avoid excessive pollution of the atmosphere.Furthermore, nitrogenous compounds interfere with the desired reactionsin both catalytic and hydrocracking processes. Therefore, the preferredoperating conditions within the gas oil reaction zone (reactor 8) are apressure within the range of about 1000 to about 3000-p.s.i.g., atemperature of from about 700 F. to about 800 F., a liquid hourly spacevelocity of from 0.25 to about 3.0. At these conditions, it is possibleto produce a hydrorefined gas oil fraction containing less than about 50p.p.m. of total nitrogen, approximately 0.01% by weight of sulfur, andabout 30.0% by volume of aromatic hydrocarbons.

Similarly, With respect to the kerosene reaction zone, reactor 20, andprocessing a charge having an initial boiling point of about 300 F. toabout 450 F., the operating severity is of a lesser degree than in theprevious reaction zone. Since kerosene product fractions, or lightdistillates, are normally employed as distillate fuels for heating andlighting, they must also be relatively low in nitrogen and sulfurconcentration, but still lower in aromatic concentration, the latter forthe purposes of improved burning characteristics in that the greater theconcentration of aromatic hydrocarbons, the lower the temperature atwhich the fuel will result in voluminous quantities of thick, oilysmoke. Thus, the operating conditions must necessarily be tailored toproduce a kerosene product low in nitrogen, low in sulfur andparticularly low in aromatic concentration 15.0% by volume or less). Bythe same token, operating conditions of a severity which would promoteboth thermal cracking and hydrocracking of the lower-boilinghydrocarbons must necessarily be avoided in order that the liquid yieldof acceptable product is economicaL- Therefore, although the operatingpressure in reactor 20 may be identical to that in reactor 8, theoperating temperature is generally lower and will be within the range ofabout 600 F. to about 750 F., the liquid hourly space velocity beinghigher, from about 0.5 to about 5.0.

With respect to the naphtha, or gasoline fraction processed in reactor30, the gasoline product efiluent must not only be substantiallycompletely free from nitrogenous and sulfurous compounds, but should besubstantially free from olefinic and high-olefinic hydrocarbons. Thus,the primary function of gasoline reactor 30 is hydrogenativehydrorefining accompanied by minimum hydrocracking. Therefore, theoperating pressure is at a lower level than in the first two reactionzones, being within the range of about 500 to about 1500 p.s.i.g., theoperating temperature somewhat higher, and within the range 'of about700 F. to about 800 F., whereas the liquid hourly space velocity ishigher than in either the first or second reaction zones, within therange of about 1.5 to about 10.0. Under these conditions, a naphthacharge stock having an initial boiling point of about 130 F. and an endboiling point of about 375 F., containing about 105 p.p.m. of nitrogen,1.6% by weight of sulfur and about 30.0% by volume of olefins, can beprocessed to'yield a hydrorefined gasoline product containing less thanabout 0.1 p.p.m. of nitrogen, 0.0005 by weight of sulfur and only atrace quantity of olefinic hydrocarbons. Such a charge stock, as will berecognized, is ideally suited for further processing in a catalyticreforming unit. Although at least a portion of the gasoline boilingrange aromatics may be hydrogenated to the corresponding naphthenichydrocarbons in this third reaction zone, such a result is notnecessarily detrimental. As hereinbefore set forth, the gasoline productfrom fractionator 35 is intended as charge to a catalytic reformingprocess, one of the main reactions of which is the dehydrogenation ofnaphthenes to the corre sponding aromatic hydrocarbons. Thus, a naphthaproduct fraction containing about 30.0% naphthenes, 8.0% aromatics and62.0% parafiins is considered a valuable product notwithstanding that upto about 50.0% of the aromatics originally present in the naphtha chargehave been hydrogenated to the corresponding naphthenes.

Just as the cascade system of effecting the hydrorefining processpermits varying the operating conditions to conform to thecharacteristics of the charge stock to each zone, the catalyticcomposite disposed within each reaction zone may be of a compositionconducive to producing greater yields of the desired product efiiuent.On the other hand, the hydrorefining catalytic composite disposed withineach of the reaction zones, represented by reactors 8, 20 and 30, maypossess the same physical characteristics and be of the same chemicalcomposition. Thus, the catalytic composite, for utilization in thecascade system of the process of the present invention will be acomposite of a siliceous refractory inorganic oxide carrier material andat least one metallic component selected from the metals and compoundsof Groups VI-B and VIII of the Periodic Table. In this regard, aparticular catalytic composite, suitable for utilization in all thereaction zones, comprises a carrier material of about 88.0% by weight ofalumina and 12.0% by weight of silica. With this siliceous carriermaterial, there is com posited about 11.3% by weight of molybdenum, 4.2%by weight of nickel and a minor amount of cobalt, about 0.05% by weight.Although existing as sulfides, or lower oxides thereof,the'catalytically active metallic components are computed as if existingin the form of the elemental metals.

As hereinbefore set forth in the various embodiments of the presentinvention, the hydrorefining catalytic composite, possessing a finitedegree of hydrocracking activity, comprises at least one metalliccomponent selected from the metals and compounds of Groups VI-B and VIIIof the Periodic Table. With respect to the use of the term, Groups VI-Band VIII, reference is made to the Periodic Chart of the Elements,Fischer Scientific Company, 1953. Suitable hydrorefining catalyticcomposites include, therefore, at least one or more metals or compoundsfrom the group of chromium, molybdenum, tungsten, iron, cobalt, nickel,palladium, platinum, ruthenium, rhodium, osmium, iridium, and mixturesthereof, etc. The total quantity of metallic components, computed as theelemental metals, will be within the range of from about 0.01% to about30.0% by weight, on the basis of the total composite. The Group VI-Bmetal, such as chromium, molydbenum, or tungsten, is usually presentwithin the range of from about 10.0% to about 30.0% by weight. The GroupVIII metals, which may be conveniently divided into sub-groups, arepresent in an amount of from about 0.01% to about 10.0% by weight of thetotal catalyst. When an iron-group metal, such as iron, cobalt, ornickel, is employed, it is present in an amount of from about 0.01% toabout 10.0% by weight, while if a plati- 'num-group metal, such asplatinum, palladium, iridium osmium, etc., is employed, it is presentwithin an amount within the range of from about 0.01% to 5.0% by weightof the total catalyst. Therefore, suitable catalysts for utilization inthe process of the present invention, include, but are not considered tobe limited to, the following: 11.3% by weight of molybdenum, 4.2% byweight of nickel and 0.05 by weight of cobalt; 16.0% by weight ofmolybdenum and 1.8% by weight of nickel; 6.0% by weight of nickel and0.2% by weight of palladium; 0.4%

by weight of palladium; 0.4% by weight of ruthenium and 11.3% by weightof molybdenum; 0.4% by weight of platinum, etc. As hereinafterindicated, it is preferred to utilize as siliceous carrier material withwhich is combined from about 10.0% to about 30.0% by weight ofmolybdenum and from about 1.0% to about 6.0% by weight of nickel. It hasbeen found that this particularly preferred catalytic composite yieldsthe most advantageous'results with respect to the greater majority ofcharge stock types and varied product distributions.

The carrier material for utilization in a hydrorefining catalyticcomposite of the present process comprises silica and one or more otherrefractory inorganic oxides including alumina, zirconia, thoria, boria,hafnia, magnesia, strontia, etc., and may he naturally-occurring orsynthetically-prepared. When synthetically-prepared, the carriermaterial may be made in any suitable manner including separate,successive or coprecipitation methods. For example, silica may beprepared by comrningling water glass in a mineral acid under suchconditions as will precipitate a silica hydrogel. The silica hydrogel issubsequently Washed with water containing a small amount of a suitableelectrolyte for the purpose of removing residual sodium ions. The oxidesof other compounds, when desired, may be prepared by reacting a basicreagent such as ammonium hydroxide, ammonium carbonate, etc., with anacid-salt solution of the metal, as for example, the chloride, sulfate,nitrate, etc., or by adding an acidic reagent to an alkaline salt of ametal such as for example, commingling sulfuric acid with sodiumaluminate, etc. When it is advantageous to prepare the carrier materialin the form of particles of uniform size and shape, this may be readilyaccomplished by grinding the partially dried oxide cake, with a suitablelubricant such as steric acid, resin, graphite, polyvinyl alcohol, etc.,subsequently forming the particles in any suitable pelleting orextrusion apparatus. The preferred carrier material, for utilizationherein, comprises alumina and silica, and such a composite may beprepared by separate precipitation methods, in which the oxidesprecipitated separately, and then mixed while in the wet state; whensuccessive precipitation methods are employed, the first oxide isprecipitated as previously set forth, and the wet slurry, either with orwithout prior washing, is composited with a salt of the other component.Thus, a precipitated, hydrated silica, substantially alkaline-free issuspended in an aqueous solution of aluminum chloride and/or zirconiumchloride following which, precipitated hydrated alumina and precipitatedhydrated zirconia are composited upon the silica gel through theaddition of an alkaline precipitant such as ammonium hydroxide. Theresulting mass of hydrated oxide is water washed, dried and calcined atabout 1400 F. Another possible method of manufacturing consists ofcommingling an acid such as hydrochloric acid with commerical waterglass under conditions to precipitate silica, washing the precipitatewith the acidulated water or other means to remove sodium ions, andcommingling with an aluminum salt such as aluminum chloride and addingammonium hydroxide to precipitate alumina or forming the desired oxideor oxides through the thermal decomposition of the salt as the case maypermit. It is understood that the particular means employed for themanufacture of the catalytic composite is not considered to be alimiting feature of the cascade process of the present invention, andsuch methods of manufacture are herein presented for the sole purpose ofillustration and completeness. The carrier material particles likewisetake the form of any desired shape such as spheres, pills, pellets,cakes extrudates, powder, granules, briquettes, etc. A particularlypreferred form is the sphere, and shperes may be continuouslymanufactured by passing droplets of a hydrosol into an oil bath which ismaintained at eleveated temperature, retaining the droplets in said oilbath until the same set into firm hydrogel spheriods. This particularmethod, commonly referred 16 to as the oil-drop method, is described indetail in US. Patent No. 2,620,314, issued to James Hoekstra.

Following the formation of the carrier material, the catalyticallyactive metallic components are composited therewith. The catalyticcomposite comprises at least one metallic component selected from themetals and compounds of Groups VIB and VIII of the Periodic Table, andinclude the platinum-group metals, the iron-group metals, molybdenum,tungsten, and chromium. These components may be incorporated within thealumina-silica carrier material in any suitable manner, although animpregnating technique is particularly convenient, and is preferred.Such a technique involves first forming an aqueous solution of awater-soluble compound of the desired metals such as molybdic acid,platinum chloride, palladium chloride, chloropla-tinic acid, ammoniummolybdate, nickel nitrate hexahydrate, tungsten chloride,dinit-ritod-iamino platinum, etc., commingling the resulting solutionwith the alumina-silica in a stream dryer. Where the metallic compoundis not water-soluble at the chosen impregnating temperature, othersuitable solvents such as a'lcohols, ethers, etc., may be employed. Thefinal composite, after all the catalytic components are presentthe-rein, is dried for a period of from about 2 to about 8 hours ormore, and subsequently oxidized or calcined in an atmosphere of air atan elevated temperature within the range of about 1100 F. to about 1700F., and for a period of from about 1 to about 8 hours or more. Followingthe high-temperature calcination treatment, the catalyst may be furthertreated for the purpose of converting the greater proportion of thecatalytically active metallic components to a particularly desired form.Thus, the final catalytic composite may contain the active met-alliccomponents in the form of oxides, sulfides, as a complex with thealumina and silica or both, or in the most reduced state.

In many instances, the catalytic composite disposed within the firstreaction zone (react-or 8 in the drawing) will contain a greaterconcentration of silica and a lesser concentration of nickel than thecatalytic composite disposed in the second and third reaction zones(reactors 20 and 30 in the drawing). For example, where the charge stockto the first reaction zone is predominant in hydrocarbons boiling abovea temperature of about 650 F., the catalyst will comprise from about12.0% to about 40.0% by weight of silica, from about 10.0% to about30.0% by weight of molybdenum and from about 1.0% to about 4.5% byweight of nickel. Similarly, the charge stock to the second reactionzone consists predominantly of those hydrocarbons boiling within therange of about 400 F. to about 650 F., and the catalyst disposed thereincomprises from about 10.0% to about 25.0% by weight of silica, alumina,from about 10.0% to about 30.0% by weight of molybdenum and from about1.5% to about 6.0% by weight of nickel. In view of the fact that thecharge stock to the third reaction zone (reactor 30 in the drawing)comprises essentially gasoline boiling range hydrocarbons, it ispreferred to utilize a catalytic composite having a somewhat lesserdegree of hydrocracking activity, but a relatively strong activity foreffecting hydrorefining reactions, and particularly the hydrogenation ofmonoand diolefinic hydrocarbons. Therefore, the catalyst disposed withinthe third reaction zone will generally comprise alumina, from 10.0% toabout 25.0% by weight of silica, 10.0% to about 30.0% by weight ofmolybdenum and from about 1.5 to about 6.0% by weight of nickel.

When utilizing the continuous-type process flow, which is theparticularly preferred manner of effecting the present invention, thevarious catalytic composites may be disposed in their respectivereaction zones as fixed beds, as illustrated in the accompanyingdrawing, and maintained therein under the desired opera-ting conditions.As illustrated, the charge to each of the reaction zones passes threthrough in dowhflow; where desired, the internals of the reactionzones may be designed to permit radial flow through the catalyst bed.The operation may also be effected as -a moving-bed type, or asuspensoid-type of operation in which the catalyst and hydrocarbons arepassed as a slurry through the reaction zone, or as a combinationprocess of moving-bed, fixed-bed and/or suspensoid-type.

When processing a full boiling range hydrocarbon charge stock, inaccordance with the cascade system, complete control is available withrespect to the degree of hydrogenation and hydrocracking, and,therefore, highly desirable control in regard to the properties of theintended product fractions. If the entire charge were processed in asingle reactor, or in an uninterrupted series, extremely high severity,particularly in terms of pressure, space velocity (lower levels) andhydrogen circulation, would be required in order to meet simultaneouslythe specifications set upon all the given fractions of the entireproduct. Extreme operating severity necessarily results in an excessivedegree of hydrocracking, whereby large quantities of normally gaseousmaterial are produced at the expense of the more valuable liquidhydrocarbons,

and over-hydrogenation whereby a greater quantity of aromatics aresaturated than is necessary, in turn increasing hydrogen consumpetion.Of greater importance is the fact that significantly lesser yields ofgas oil and kerosene fractions are realized. If the total full boilingrange charge stock were to be processed in a single reactor, and at suchconditions as to produce a suitable gas oil boiling range specificationproduct, with the resulting kerosene and naphtha fraction in turncharged to a second, in series, reactor, operated to produce a suitablekerosene boiling range specification product, and again followed by afraction-ator to produce a naphtha, or gasoline boiling range charge toanother-reactor system for the production of specific naphtha, many moretotal barrels of combined feed would be processed than had the cascadesystem been employed. Furthermore, a significantly greater quantity ofcatalyst would be required where the process is eifected inuninterrupted series flow. It is, therefore, evident that the cascadescheme results in lower initial investment and operating costs, whileproducing significantly higher yields of normally liquid hydrocarbonproduct.

The following example is given to further illustrate the cascade systemof the process of the present invention, and to indicate the benefits tobe afiorded through the utilization thereof. It is not intended to limitunduly the present invention to the charge stock, catalyst, operatingconditions, product specifications, etc., as set forth. It is understoodthat the example is given for the sole purpose of illustration, and isnot intended to limit the generally broad scope and spirit of theappended claims.

EXAMPLE In this example, the catalytic composite disposed in all threeof the reaction zones was -inch spherical particles of 88.0% by weightof alumina and 12.0% by weight of silica, containing 0.05% by weight ofcobalt (based upon the weight of the finished catalyst). Thecatalytically active metallic components were added to thecobaltcontaining carrier material by commingling molybdic acid (85.0% byweight of molybdic oxide) and nickel nitrate hexahydrate to form theimpregnating solution which was intimately commingled with thepreviously prepared cobalt-containing carrier material. The molybdicacid was utilized in an amount to result in a catalytic compositecomprising 11.3% by weight of molybdenum, the nickel nitrate hexahydratebeing utilized to result in 4.2% by weight of nickel, computed on thebasis of the elemental metals. The impregnated alumina-silica sphereswere then dried for a period of about three hours at a temperature ofabout 300 F., the temperature being increased to 1100 F., and thecomposite calcined in an atmosphere of air for a period of about onehour at the elevated temperature.

The charge stock was a full boiling range coker distillate having aninitial boiling point of about 130 F. and an end boiling point of about825 F. This distillate was originally derived from a hydrocarbonaceousheavy oil (extracted from Athabaska Oil Sands), when the latter wasfirst processed in a coking unit, and, as such, contained a largequantity of aromatic hydrocarbons boiling above about 500 F. and a highconcentration of olefinic hydrocarbons boiling below about 500 F. Fromthis full boiling range coker distillate, it was desired to producethree individual hydrocarbon fractions having particular, specificproperties. Specifications required the production of a gas oil fractionhaving an initial boiling point of about 500 F., and containing lessthan about 0.1% by weight of sulfur, less than 500 ppm. of totalnitrogen and a maximum of 30.0% by volume of aromatic hydrocarbons; akerosene fraction, having a boiling range of from about 375 F. to about500 F., was required to contain less than about 0.05 weight percentsulfur, less than about 50 p.p.m. of total nitrogen, and less than about15.0 volume percent aromatic hydrocarbons; the specified productproperties were significantly more stringent with respect to a naphthafraction having an end boiling point of about 375 F., being less than6.0 ppm. of sulfur and less than 1.0 p.p.m. of total nitrogen. Withrespect to the naphtha fraction, since this particular product wasintended for subsequent utilization as the charge stock for a catalyticreforming unit, the concentration of olefinic hydrocarbons therein wasrequired to be substantially nil.

The full boiling range coker distillate was initially separated bydistillation for the purpose of providing the individual raw fractions,each of which was intended for use as charge to a hydrorefining reactionzone. These three initial fractions were, a gas oil fraction, having aninitial boiling point of about 515 F. and an end boiling point of about826 F.; a kerosene fraction having an initial boiling point of about 380F. and an end boiling point of about 536 F.; a naphtha fraction, orgasoline fraction having an initial boiling point of about 133 F. and anend boiling point of about 368 F. Other significant properties of thesethree fractions are presented in the following Table I.

TABLE L-OHARGE STOCK PROPERTIES-INITIAL FRACTIONS Fraction Gas OilKerosene Naphtha V01. Percent of Distillate 53. 9 20. 4 25. 7 Gravity,API at 60 F 18. 3 32. 9 54. 5 100 ml. ASTM Distillation, F.:

Initial Boiling Point 515 380 133 5% 530 396 168 10% 550 409 188 30% 600428 236 50% 645 441 272 70%- 697 458 297 780 477 342 807 490 357 EndBoiling Poii 826 536 368 Component Analysis, Vol. Percen Aromatics 62. 139. 2 16. 9 Olefin; 2. 0 l4. 4 30. 8 Paraifins and Naphthenes 35. 9 46.4 52. 3 Sulfur, Wt. Percent 3. 3 2. 4 1.6 Total Nitrogen, p.p.m 1, 530340 Bromine Number 18.0 36.0 61.0

The first reaction zone contained 400 cc. of the catalytic compositehereinbefore described, disposed therein in eight individual catalystbeds of 50 cc. each. The reaction zone was maintained at a pressure ofabout 1500 p.s.i.g. and the inlet temperature thereto controlled suchthat the maximum catalyst temperature during processing attained a levelof 760 F. Hydrogen circulation, by way of compressive means, was in anamount of 3840 s.c.f./bbl., the hydrogen being admixed with the gas oilentering the reaction zone at a rate of 218 cc. per hour. Thus, theliquid hourly space velocity, defined as volumes of liquid hydrocarboncharge per hour per volume of catalyst disposed within the reactionzone, was 0.54.

Following a suitable interval of stable, lined-out operation, a testperiod of about 12 hours duration was performed, during which timesamples of the product gaseous phase and normally liquid portion of theproduct efliuent were obtained. The normally liquid portion of theproduct effiuent was fractionated in a distillation column at acut-point of about 500 F. Both the gas oil product, having an initialboiling point of about 505 F. and an end boiling point of about 784 F.,and the synthetic kerosene fraction, having an initial boiling point ofabout 180 F. and an end boiling point of about 492 F., were subjected toanalysis to determine the character of the various components, and theconcentration of the contaminating influences. Analyses on the gas oiland synthetic kerosene fractions are presented in the following TableII; included in this table is the tabulation of the product distributionof the total reaction zone efliuent.

TABLE II.-IRODUOT ANALYSIS AND DISTRIBUTION GAS OIL Fraction Gas OilSynthetic Product Kerosene Gravity, API at 60 F 28. 39. 8 100 ml. ASIMDistillation, F.:

Initial Boiling Point 505 180 540 239 550 270 30%-- 578 352 50%-. 600400 70%.- 650 42s 90%.- 715 452 95% 753 401 End Boiling Point 784 402Component Analysis, Vol. Percent:

Aromatics 30. 1 32. 0 1. 0 2. 5 68. 9 65. 5 Sulfur, Wt. Percent 0. 00970.0001 Total Nitrogen p.p.m.. 14. 0 0. 4 Bromine Number 0.9 2. 2

Product distribution, total effluent:

Hydrogen consumption, s.c.f./bbl. 1262 Light paraffinic hydrocarbons,wt. percent:

Methane 0.4 Ethane 0.6 Propane 0.8 Liquid yields, vol. percent:

Total butanes 1.3 Total pentanes 0.2 Hexanes and heavier 102.2 C to 500F 23.8 500 F. to end point 78.6

With reference to Table II, it will be noted that the specificationsplaced upon the gas oil product were achieved. The primary concern wasthe concentration of aromatics, and this decreased from a level of 62.1volumetric percent to 30.1 volume percent. Of further significance isthe fact that both the gas oil and synthetic kerosene fractions weresubstantially completely free from the contaminating influence of sulfurand nitrogenous compounds, and the chemical hydrogen consumption wasonly 1262 s.c.f./bbl., or 1.6% by weight of the raw gas oil charge.There was an incease in liquid yield of about 2.2 volume percent, basedupon liquid charge, not including the total butanes and pentanesresulting from the selective hydrocrac'king of the heavier components.The synthetic kerosene fraction, C to 500 F. end boiling point, wasproduced in an amount of 23.8 volume percent, while the gas oil productwas produced in an amount of 78.6 volumetric percent.

As hereinbefore set forth in a preferred embodiment, the synthetickerosene fraction resulting from the original gas oil charge wouldnormally be cut at an initial boiling point of about 300 F. to about 450F., to provide a synthetic naphtha having an end boiling point withinthis range. That is to say, the total product efiiuent from the gas oilreaction zone would be fractionated to provide three individualfractions rather than the two fractions hereinabove described. However,in view of the specified properties on the kerosene and naphtha productfractions, it was expedient in the small pilot plant scale unit toeliminate this extra fractionation step and the accompanying necessaryanalyses. In a commercial size unit, charging up to as high as about20,000 barrels per day, particularly where the kerosene fraction hadboth a higher initial boiling point and end boiling point, the total gasoil product effluent would be fractionated to provide both the syntheticnaphtha and synthetic kerosene fractions.

The synthetic kerosene fraction, as produced, was combined with theinitial kerosene fraction, the combined kerosene charge having theproperties indicated in the following Table III.

TABLE III.KEROSENE CHARGE AND PRODUCT ANALYSIS Fraction KeroseneKerosene Synthetic Charge Product Naphtlia Gravity, API at 60 F 35.4 38.5 50. 2 100 ml. ASTM Distillation, F.:

Initial Boiling Point- 230 378 178 5% 293 397 21s 10% 354 4.08 230 30%-410 424 263 50%- 432 434 28G 70%. 450 447 308 473 472 330 484 483 336End Boiling Point- 510 525 367 Component Analysis, Vol.

Percent:

Aromatics 3e. 3 15. 0 17. 2 9. (i 0 0 54.1 85.0 82. s Sulfur, Wt.Percent 1.5 0.0001 0. 0001 Total Nitrogen, p.p.1n... 204 0. 2 1. 7Bromine Number 0. 0144 0.0110

Product distribution, total effluent:

Hydrogen consumption, s.c.f./bbl. 591 Light paraffinic hydrocarbons, wt.percent:

Methane 0.05 Ethane 0.05 Propane 0.1 Liquid yields, vol. percent:

Total butanes 0.2 Total pentanes 0.4 Hexanes and heavier 100.5 C to 375F 20.3 375 F. to end point 80.6

On a volumetric basis, the combined kerosene charge consisted of 60.0%of the initial raw fraction, and about 40.0% of the synthetic kerosenefraction. The combined kerosene charge was admixed with a hydrogen-richrecycle gas stream in an amount of about 4330 s.c.f./bbl., the mixturepassing into a second reaction zone maintained at a pressure of about1500 p.s.i.g. The second reaction zone contained a total of 400 cc. ofthe catalytic composite hereinbefore described, disposed therein ineight catalyst beds of 50 cc. each; based upon a charge rate of about391 cc. per hour, the liquid hourly space velocity throughout a 12-hourtest period was about 0.98. The inlet temperature to the catalyst bedwas maintained at a level such that the maximum catalyst temperaturethroughout the test period was about 653 F.

The total product effluent from the second reaction zone was separatedto provide a gaseous phase and a normally liquid hydrocarbon product.The latter was passed into a distillation column, and fractionatedtherein to provide a kerosene product having an initial boiling point ofabout 375 F. and a synthetic naphtha fraction having an end boilingpoint of about 375 F. Analyses of the two liquid product fractions, aswell as the product distribution of the total hydrocarbonaceousefliuent, are also given in the foregoing Table III. It will be notedthat the specified properties placed upon the kerosene product fractionhave been met, and that the product is virtually completely devoid ofsulfurous and nitrogenous compounds. The kerosene product obtained fromthe 12-hour test period contained about 15.0 volume percent of aromatichydrocarbons as indicated in Table III. However, it must be stated thatthe product-obtained both before and after the test period, andincluding that portion obtained during the test period (a total quantityof about 30 gallons), contained 13.8 volume percent aromatics,significantly below the specified quantity. Of further interest, asindicated in Table III, is the fact that the chemical hydrogenconsumption was only 591 s.c.f./bbl., or 1.0% by weight of the totalkerosene charge. As indicated by the product distribution, on the totalliquid efiluent, there was an increase in liquid yield of 0.5 volumepercent, not counting butanes and pentanes.

The synthetic naphtha was combined with the original raw naphthafraction, and passed into the third reaction zone containing 100 cc. ofthe catalytic composite hereinbefore described, disposed in fiveindividual beds of 20 cc. each: The recycle hydrogen rate was 3327s.c.f./bbl. The reaction zone was maintained at a pressure of about 800p.s.i.g., the inlet temperature to the catalyst being controlled toresult in a maximum catalyst bed temperature of 747 F. Based upon aliquid charge rate of about 243 cc. per hour, the liquid hourly spacevelocity was 2.43. Analyses of the combined naphtha charge and thenormally liquid product efliuent are given in the following Table IV.

TABLE IV.NAPHIHA CHAR GE AND PRODUCT ANALYSIS Fraction Naphtha NaphthaCharge Product Gravity, API at 60 F 52. 8 58. 3 100 ml. ASTMDistillation,

Initial Boiling Point 124 124 5% 170 167 192 187 30%--. 243 230 50%- 277205 70%- 309 303 90%. 343 343 95% 346 360 End Boiling Point 378 388Component Analysis, Vol. Percent:

Aromatics 18. 6 8. 0 Olefius 25. 2 Trace Parafiins and Naphthenes- 92. 0Sulfur, Wt. Percent. 0. 0005 Total Nitrogen, ppm 0. 1 Bromine Number. 0.0174 Product distribution, total efiluent:

Hydrogen consumption, s.c.f./bbl. 497 Light paraffinic hydrocarbons, wt.percent:

Methane 0 Ethane 0.1 Propane 0.2 Liquid yields, vol. percent:

Total butanes 1.3 Total pentanes 4.1 Hexanes and heavier 97.9

Total pentanes and heavier 102.0

With reference to Table IV, it will be noted that the naphtha productconstitutes a highly desirable charge for a subsequent catalyticreforming unit. The liquid consists essentially of aromatics, parafiinsand naphthenes, the concentration of olefinic hydrocarbons being intrace quantities only. The contaminating influence of sulfur andnitrogen is virtually non-existent, being 0.0005 by Weight and 0.1 ppm.respectively. While processing the combined naphtha charge, only 497s.c.f./bbl. of hydrogen was consumed, and only 0.3% by weight of thecharge stock was converted into light paralfinic hydrocarbons generallyconsidered as waste material. Including the butanes and pentanesproduced, the liquid yield was 2.0 volume percent greater than the totalcharge to the third reaction zone.

With reference to the data tabulated in the foregoing Tables I, II, IIIand IV, several unexpected, extremely Ill beneficial results should beimmediately recognized. That these results are unusual is evident whenconsidering the characteristics of the charge stock and the specifiedproperties imposed upon the individual fractions to be derivedtherefrom. Of prime consideration, economically, is the fact thatbetween about 3.0 and 4.0 volume percent more liquid hydrocarbons areproduced than are charged to the overall system; this volumetricincrease is of itself unusual in view of the fact that the overallchemical hydrogen consumption, computed on the basis of the total cokerdistillate, is only slightly higher than 1025 s.c.f./bbl. Furthermore,the weight percent loss to light paraflinic hydrocarbons (methane,ethane and propane) is only about 2.0. As hereinbefore set forth, suchresults could not be achieved by present-day hydrorefining processeswhich incorporate in-series reactor systems.

I claim as my invention:

1. A process for hydrorefining a hydrocarbon charge stock comprisinghydrocarbons boiling above the gasoline boiling range, and containing acontaminant selected from the group consisting of nitrogenous compoundsand sulfurous compounds, which process comprises the steps of:

(a) hydrocracking and hydrorefining said charge stock in admixture withhydrogen at a temperature in the range of from about 600 F. to about 350F. in a first reaction zone containing a hydrorefining catalyticcomposite;

(b) separating the normally liquid product efiluent from said firstreaction zone into a first light fraction, having an end boiling pointof from about 400 F. to about 650 F. and a heavier fraction;

(c) combining at least a portion of said first light fraction with ahydrocarbon mixture having an initial boiling point of from about 300 F.to about 450 F. and containing at least one of the aforesaidcontaminants, and reacting the resulting mixture with hydrogen at atemperature within said range in a second reaction zone containing ahydrorefining catalytic composite and maintained under less severeconversion conditions than said first zone;

(d) separating the normally liquid product effluent from said secondreaction zone into a second light fraction, having an end boiling pointwithin the range of from about 300 F. to about 450 F., and ahydrorefined second heavy fraction;

(e) combining at least a portion of said second light fraction with ahydrocarbon mixture, having an end boiling point of from 300 F. to about450 F. and containing at least one of the aforesaid contaminants,reacting the resulting mixture with hydrogen at a temperature withinsaid range in a third reaction zone containing a hydrorefiniug catalyticcomposite and maintained under conditions to effect hydrogenativehydrorefining of said mixture with minimum hydrocracking; and,

(f) separating the product efiiuent from said third reaction zone into anormally gaseous phase and a hydrorefined third heavy fraction.

2. The process of claim 1 further characterized in that at least aportion of said first light fraction is combined with said second lightfraction and a hydrocarbon mixture having an end boiling point of fromabout 300 F. to about 450 F. prior to reacting the latter with hydrogenin said third reaction zone.

3. A process for hydrorefining a hydrocarbon charge stock comprisinghydrocarbons boiling within and above the gasoline boiling range, andcontaining sulfurous and nitrogenous compounds, which process comprisesthe steps of:

(a) separating said charge stock into a gasoline fraction having an endboiling point within the range of from about 300 F. to about 450 F., akerosene fraction having an end boiling point of from 400 F. to about650 F., and a heavy bottoms fraction;

(b) hydrocracking and hydrorefining said heavy bottoms fraction inadmixture with hydrogen at a temperature in the range of from about 600F. to about 850 F. in a first reaction zone containing a hydrorefiningcatalytic composite;

(c) separating the normally liquid product efiluent from said firstreaction zone into a first light fraction having an end boiling point offrom about 300 F. to about 450 F. and a second light fraction having anend boiling point of from about 400 F. to about 650 F and ahydrorefined, substantially sulfur-free heavy fraction;

(d) combining at least a portion of said second light fraction with theaforesaid kerosene fraction and reacting the resulting mixture withhydrogen at a temperature wit-bin said range but lower than thatmaintained in said first zone to convert nitrogenous and sulfurouscompounds to ammonia, hydrogen sulfide and hydrocarbons, in a secondreaction zone containing a hydrorefining catalytic composite;

(e) separating the normally liquid product effiuent from said secondreaction zone into a third light fraction having an end boiling point offrom about 300 F. to about 450 F. and a hydrorefined, substantiallysulfur-free kerosene product;

(f) combining at least a portion of each of said first and third lightfractions with the aforesaid gasoline fraction and reacting theresulting mixture with hydrogen at a temperature within said range in athird reaction zone containing a hydrorefining catalytic composite andmaintained under conditions to effect hydrogenative hydrorefining ofsaid mixture with minimum hydrocracking; and,

(g) separating the product effluent from said third reaction zone into anormally gaseous phase and a substantially sulfur and nitrogen-freehydrorefined gasoline product.

4. A process for hydrorefining a hydrocarbon charge stock comprisinghydrocarbons boiling within and above the gasoline boiling range, andcontaining sulfurous and nitrogenous compounds, which process comprisesthe steps of:

(a) separating said charge stock into a gasoline fraction having an endboiling point Within the range of from about 350 F. to about 450 F., akerosene fraction having an end boiling point of from about 500 F. toabout 650 F., and a heavy bottoms fraction;

(b) hydrocracking and hydrorefining said heavy bottoms fraction inadmixture with hydrogen at a temperature in the range of from about 600F. to about 850 F. in a first reaction zone containing a hydrorefiningcatalytic composite;

(c) separating the normally liquid product efiluent from said firstreaction zone into a first light fraction having an end boiling point offrom about 350 F. to about 450 F. and a second light fraction having anend boiling point of from about 500 F. to about 650 F. and ahydrorefined, substantially sulfur-free heavy fraction;

(d) combining at least a portion of said second light fraction with theaforesaid kerosene fraction and reacting the resulting mixture withhydrogen at hydrorefining conditions selected to convert nitrogenous andsulfurous compounds to ammonia, hydrogen sulfide and hydrocarbons, in asecond reaction zone containing a hydrorefining catalytic composite andmaintained at a temperature within said range;

(e) separating the normally liquid product efiluent from said secondreaction zone into a third light fraction having an end boiling point offrom about 350 F. to about 450 F. and a hydrorefined, substantiallysulfur-free kerosene product;

(f) combining at least a portion of each of said first and third lightfractions with the aforesaid gasoline fraction and reacting theresulting mixture with hydrogen at hydrorefining conditions selected toconvert nitrogenous and sulfurous compounds to ammonia, hydrogen sulfideand hydrocarbons in a third reaction zone containing a hydrorefiningcatalytic composite and maintained at a temperature Within said range;and,

(g) separating the product effluent from said third reaction zone into anormally gaseous phase and a substantially sulfur and nitrogen-freehydrorefined gasoline product.

5 The process of claim 4 further characterized in that the conversionconditions include a liquid hourly space velocity within the range offrom about 0.25 to about 10.0 in each of said three reaction zones.

6. The process of claim 4 further characterized in that the conversionconditions include a pressure of from about 500 to about 5000 p.s.i.g.,in each of said three reaction zones.

'7. The process of claim 4 further characterized in that the maximumcatalyst temperature in said second reaction zone is less than themaximum catalyst temperature in said first reaction zone.

8. The process of claim 5 further characterized in that the liquidhourly space velocity in said first reaction zone is less than that insaid second and third reaction zones, and the liquid hourly spacevelocity in said second reaction zone is less than that in said thirdreaction zone.

9. A process for hydrorefining a hydrocarbon charge stock comprisinghydrocarbons boiling Within and above the gasoline boiling range andcontaining sulfurous and nitrogenous compounds, Which process comprisesthe steps of:

(a) separating said charge stock into a gasoline fraction having an endboiling point Within the range of from about 350 F. to about 450 F., akerosene fraction having an end boiling point of from about 500 F. toabout 650 F., and a heavy bottoms fraction;

(b) hydrocracking and hydrorefining said heavy fraction in admixturewith hydrogen present in an amount of from about 1000 to about 6000s.c.f./ bbl., at a temperature in the range of from about 600 F. toabout 850 F. in a first reaction zone containing a siliceoushydrorefining catalytic composite;

(c) separating the normally liquid product efliuent from said firstreaction zone into a first light fraction having an end boiling point offrom about 350 F. to about 450 F., a second light fraction having an endboiling point of from about 500 F. to about 650 F. and a hydrorefined,substantially sulfur-free heavy fraction;

(d) COmbining at least a portion of said second light fraction with theaforesaid kerosene fraction and reacting the resulting mixture withhydrogen present in an amount of from about 1000 to about 6000s.c.f./bbl., at hydrorefining conditions selected to convert nitrogenousand sulfurous compounds to ammonia, hydrogen sulfide and hydrocarbons,in a second reaction zone containing a siliceous hydrorefining catalyticcomposite and maintained at a temperature within said range;

(e) separating the normally liquid product efiiuent from said secondreaction zone into a third light fraction having an end boiling point offrom about 350 to about 450 F. and a hydrorefined, substan tiallysulfur-free kerosene product;

(f) combining at least a portion of each of said first and third lightfractions with the aforesaid gasoline fraction and reacting theresulting mixture with hydrogen present in an amount of from about 1000to about 6000 s.c.f./bbl., at hydrorefining conditions selected toconvert nitrogenous and sulfurous compounds to ammonia, hydrogen sulfideand hydrocarbons, in a third reaction zone containing a siliceoushydrorefining catalytic composite and maintained at a temperature withinsaid range; and

(g) separating the product effluent from said third reaction zone into anormally gaseous phase and a substantially sulfur and nitrogen-freehydrorefined gasoline product.

10. The process of claim 9 further characterized in that the catalyticcomposite in said first, second and third reaction zones is a compositeof alumina, silica and at least one metallic component selected from thegroup of metals of Groups VI-B and VII of the Periodic Table.

11. The process of claim 9 further characterized in that the catalyticcomposite in said first, second and third reaction zones is a compositeof alumina, silica, molybdenum and an iron-group metallic component.

12. The process of claim 11 further characterized in that the catalyticcomposite in said first, second and third reaction zones is a compositeof alumina, silica, from about 10.0% to about 30.0% by weight ofmolybdenum and from about 1.0% to about 6.0% by weight of nickel,calculated as the elemental metals.

13. The process of claim 12 further characterized in that the catalyticcomposite in said first reaction zone contains more silica and lessnickel than the catalytic composite in said second and third reactionzones.

14. A process for hydrorefining a full boiling range coker distillatecontaining sulfurous and nitrogenous compounds, which process comprisesthe steps of:

(a) separating said distillate into a gasoline fraction having an endboiling point within the range of from about 350 F. to about 450 F., akerosene fraction having an end boiling point of from about 500 F. toabout 650 F. and a heavy bottoms fraction having an initial boilingpoint of from about 500 F. to about 650 F.;

(b) hydrocracking and hydrorefining said heavy bottoms fraction inadmixture with hydrogen present in an amount of about 1000 to about 6000s.c.f./bbl., at -a maximum catalyst temperature within the range of fromabout 600 F. to about 850 F. in a first reaction zone containing ahydrorefining catalytic composite of alumina, from about 12.0% to about40.0% by weight of silica, molybdenum and nickel;

(c) removing hydrogen sulfide and ammonia from the product effluent fromsaid first reaction zone, separating the remaining normally liquidproduct into a first light fraction having an end boiling point of fromabout 350 F. to about 450 F., a second light fraction having an endboiling point of from 26 about 500 F. to about 650 F. and ahydrorefined, substantially sulfur-free gas oil fraction;

(d) combining at least a portion of said second light (e) removinghydrogen sulfide and ammonia from the product efiluent from said secondreaction zone, separating the remaining normally liquid product into athird light fraction having an end boiling point of from about 350 F. toabout 450 F. and a hydrorefined, substantially sulfur-free kerosenefraction;

(f) combining at least a portion of each of said first and third lightfractions with the aforesaid gasoline fraction and reacting theresulting mixture with hydrogen present in an amount of from about 1000to about 6000 s.c.f./'b=bl., at hydrorefining conditions including amaximum catalyst temperature of from about 600 F. to about 850 F. andselected to convert sulfurous and nitrogenous compounds to hydrogensulfide, ammonia and hydrocarbons, in a third reaction zone containing ahydrorefining catalytic composite of alumina, silica, molybdenum andnickel; and,

(g) separating the product effluent from said third reaction zone into anormally gaseous phase containing hydrogen sulfide and ammonia, and asubstantially sulfur and nitrogen-free hydrorefined gasoline fraction.

References Cited by the Examiner UNITED STATES PATENTS Franklin 208-210Hengstebeck 2082l0 Inwood 2082l0 Watkins 208-264 DELBERT E. GANTZ,Primaly Examiner. S. P. JONES, Assistant Examiner.

1. A PROCESS FOR HYDROREFINING A HYDROCARBON CHARGE STOCK COMPRISINGHYDROCARBON BOILONG ABOVE THE GASOLINE BOILING RANGE, AND CONTAINING ACONTAMINANT SELECTED FROM THE GROUP CONSISTING OF NITROGENOUS COMPOUNDSAND SULFUROUS COMPOUNDS, WHICH PROCESS COMPRISES THE STEPS OF: (A)HYDROCRACKING AND HYDROREFINING SAID CHARGE STOCK IN ADMIXTURE WITHHYRDOGEN AT A TEMPERATURE IN THE RANGE OF FROM ABOUT600*F. TO ABOUT850*F. IN A FIRST REACTION ZONE CONTAINING A HYDROREFINING CATALYTICCOMPOSITE; (B) SEPARATING THE NORMALLY LIQUID PRODUCT EFFLUENT FROM SAIDFIRST REACTION ZONE INTO A FIRST LIGHT FRACTION, HAVING AN END BOILINGPOINT OF FROM ABOUT 400* F. TO ABOUT 650*F. AND A HEAVIER FRACTION; (C)COMBINING AT LEAST A PORTION OF SAID FIRST LIGHT FRACTION WITH AHYDROCARBON MIXTURE HAVING AN INITIAL BOILING POINT OF FROM ABOUT 300*F.TO ABOUT 450*F. AND CONTAINING AT LEAST ONE OF THE AFORESAIDCONTAMINANTS, AND REACTING THE RESULTING MIXTURE WITH HYDROGEN AT ATEMPERATURE WITHIN SAID RANGE IN A SECOND REACTION ZONE CONTAINING AHYDROREFINING CATRALYTIC COMPOSITE AND MAINTAINED UNDER LESS SEVERECONVERSION CONDITIONS THAN SAID FIRST ZONE; (D) SEPARATING THE NORMALLYLIQUID PRODUCT EFFLUENT FROM SAID SECOND REACTION ZONE INTO A SECONDLIGHT FRACTION, HAVING AN END BOILING POINT WITHIN THE RANGE OF FROMABOUT 300*F. TO ABOUT 450*F., AND A HYDROREFINED SECOND HEAVY FRACTION;(E) COMBINING AT LEAST A PORTION OF SAID SECOND LIGHT FRACTION WITH AHYDROCARBON MIXTURE, HAVING AN END BOILING POINT OF FROM 300*F. TO ABOUT450*F. AND CONTAINING AT LEAST ONE OF THE AFORESAID CONTAMINANTS,REACTING THE RESULTING MIXTURE WITH HYDROGEN AT A TEMPERATURE WITHINSAID RANGE IN A THIRD REACTION ZONE CONTAINING A HYDROREFINING CATALYTICCOMPOSITE AND MAINTAINED UNDER CONDITIONS TO EFFECT HYDROGENATIVEHYDROREFINING OF SAID MIXTURE WITH MINIMUM HYDROCRACKING; AND, (F)SEPARATING THE PRODUCT EFFLUENT FROM SAID THIRD REACTION ZONE INTO ANORMALLY GASEOUS PHASE AND A HYDROREFINED THIRD HEAVY FRACTION.